The defenseman will be evaluated in one week, the Stars said Friday.
Polak was taken off the ice and hospitalized after he hit the boards awkwardly while attempting to check Bruins forward Chris Wagner 7:04 into the second period.
"The good news is that Roman has full use of his extremities," Dallas coach Jim Montgomery said after the game.
The Stars also lost forwards Blake Comeau and Jason Dickinson to injury.
"Comeau is going to be out multiple weeks with a lower-body injury," Montgomery said. "He got hit in the face and fell awkwardly. He strained his lower body. We know it's going to be multiple weeks. Whether that's two or four, we don't know. We'll know more tomorrow."
Comeau was injured in the first period; Dickinson did not return for the second.
"Dickinson is going to be at least a week," Montgomery said. "It's to be determined with X-rays. He got cross-checked. I don't know exactly when, but he got cross-checked and that's what caused the injury."
NHL.com independent correspondent Josh Clark contributed to this report
